This invention pertains to the segregation of used contaminated catalyst into fractions according to particle density differences, and particularly to segregating and recovering such catalysts by fluidization with light liquids using multiple concentric compartments.
In a previous design catalyst segregation process to separate used catalyst contaminated by processing of hydrocarbon feedstocks into fractions according to particle density by liquid fluidization, a single vertical cylindrical vessel was provided having a flow distributor located at the bottom end for controlling the upflowing fluidizing liquid. However, a convenient arrangement was not provided for transfer of the segregated catalyst fractions from the segregator vessel, particularly for recovery of the segregated catalyst upper fraction having lower density and less particle contamination, for reuse.
The prior art has disclosed several processes for gas fluidization of used catalyst in hydrocarbon refining and hydrocracking systems. For example, U.S. Pat. No. 2,567,207 to Hoge discloses the classification of used catalyst according to particle size by fluidization in a classifier apparatus with hot flue gas from a regeneration step. Also, U.S. Pat. No. 2,631,968 to Peery discloses separation of used catalyst by a float-sink method using a liquid which is varied in density, with the less active catalyst overflowing the separation tank into a tray from which it is passed to a filtering step for removal of the liquid. However, a process which provides for separation of a less dense, more active catalyst fraction and its convenient transfer to a further fluidization and/or recovery step for reuse is needed in the catalytic processing industry.